Pure α-latrotoxin is very inefficient at forming channels/pores in artificial lipid bilayers or in the plasma membrane of
non-secretory cells. However, the toxin induces pores efficiently in COS-7 ...cells transfected with the heptahelical receptor
latrophilin or the monotopic receptor neurexin. Signaling-deficient (truncated) mutants of latrophilin and latrophilin-neurexin
hybrids also facilitate pore induction, which correlates with toxin binding irrespective of receptor structure. This rules
out the involvement of signaling in pore formation. With any receptor, the α-latrotoxin pores are permeable to Ca 2+ and small molecules including fluorescein isothiocyanate and norepinephrine. Bound α-latrotoxin remains on the cell surface
without penetrating completely into the cytosol. Higher temperatures facilitate insertion of the toxin into the plasma membrane,
where it co-localizes with latrophilin (under all conditions) and with neurexin (in the presence of Ca 2+ ). Interestingly, on subsequent removal of Ca 2+ , α-latrotoxin dissociates from neurexin but remains in the membrane and continues to form pores. These receptor-independent
pores are inhibited by anti-α-latrotoxin antibodies. Our results indicate that (i) α-latrotoxin is a pore-forming toxin, (ii)
receptors that bind α-latrotoxin facilitate its insertion into the membrane, (iii) the receptors are not physically involved
in the pore structure, (iv) α-latrotoxin pores may be independent of the receptors, and (v) pore formation does not require
α-latrotoxin interaction with other neuronal proteins.
High-temperature polymer-electrolyte membrane fuel cells (HT-PEMFCs) are a very important type of fuel cells since they operate at 150–200 °C, making it possible to use hydrogen contaminated with CO. ...However, the need to improve the stability and other properties of gas-diffusion electrodes still impedes their distribution. Self-supporting anodes based on carbon nanofibers (CNF) are prepared using the electrospinning method from a polyacrylonitrile solution containing zirconium salt, followed by pyrolysis. After the deposition of Pt nanoparticles on the CNF surface, the composite anodes are obtained. A new self-phosphorylating polybenzimidazole of the 6F family is applied to the Pt/CNF surface to improve the triple-phase boundary, gas transport, and proton conductivity of the anode. This polymer coating ensures a continuous interface between the anode and proton-conducting membrane. The polymer is investigated using CO2 adsorption, TGA, DTA, FTIR, GPC, and gas permeability measurements. The anodes are studied using SEM, HAADF STEM, and CV. The operation of the membrane–electrode assembly in the H2/air HT-PEMFC shows that the application of the new PBI of the 6F family with good gas permeability as a coating for the CNF anodes results in an enhancement of HT-PEMFC performance, reaching 500 mW/cm2 at 1.3 A/cm2 (at 180 °C), compared with the previously studied PBI-O-PhT-P polymer.
The vitamin B1 (thiamine) structural analogue 3-decyloxycarbonylmethyl-4-methyl-5-(beta-hydroxyethyl) thiazole chloride (DMHT) (0.1 mM) reversibly reduced transmembrane currents in CaCl2 and KCl ...solutions via ionic channels produced by latrotoxins (alpha-latrotoxin (alpha-LT) and alpha-latroinsectotoxin (alpha-LIT)) from black widow spider venom and sea anemone toxin (RTX) in the bilayer lipid membranes (BLMs). Introduction of DMHT from the cis-side of BLM bathed in 10 mM CaCl2 inhibited transmembrane current by 31.6+/-3% and by 61.8+/-3% from the trans-side of BLM for alpha-LT channels. Application of DMHT in the solution of 10 mM CaCl2 to the cis-side of BLM decreased the current through the alpha-LIT and RTX channels by 52+/-4% and 50+/-5%, respectively. Addition of Cd2+ (1 mM) to the cis- or trans-side of the membrane after the DMHT-induced depression of Ca2+-current across the alpha-LT channels caused its further decrease by 85+/-5% that coincides favorably with the intensity of Cd2+ blocking in control experiments without DMHT. These data suggest that DMHT inhibiting is not specific for latrotoxin channels only and DMHT may exert its action on alpha-LT channels without considerable influence on the ionogenic groups of Ca2+-selective site inside the channel cavity. The binding kinetics of DMHT with the alpha-LT channel shows no cooperativity and allows to expect that the DMHT binding site of the toxin is formed by one ionogenic group as the slopes of inhibition rate determined in log-log coordinates are 1.25 on the trans-side and 0.68 on the cis-side. Similar pK of binding (5.4 on the trans-side and 5.7 on the cis-side) also suggest that DMHT may interact with the same high affinity site of alpha-LT channel on either side of the BLM. The comparative analysis of effective radii measured for alpha-LT, alpha-LIT and RTX channels on the cis-side (0.9 nm, 0.53 nm and 0.55 nm, correspondingly) and for alpha-LT channel on the trans-side (0.28+/-0.18 nm) with the intensity of DMHT inhibitory action obtained on these channels allowed to conclude that the potency of DMHT inhibition increased on toxin pores of smaller lumen.
Single-crystals of manganese hydroxide hydrogen vanadate divanadate, Mn
6.75
(OH)
3
H
1.20
(VO
4
)
4-2
z
(V
2
O
7
)
z
(
z
= 0.15), have been synthesized hydrothermally. Its hexagonal crystal ...structure, sp. gr.
P
6
3
mc
, related to mineral ellenbergerite, has been determined by single-crystal X-ray diffraction. It features a three-dimensional framework of vertex- and face-sharing Mn
2+
-centered octahedra with defective Mn
2+
-octahedral chains and disordered V
2
O
7
, HVO
4
and H
2
VO
4
groups located in hexagonal and triangular type channels. The presence of these groups has been confirmed by Fourier transform infrared spectroscopy. According to magnetization and specific heat data, Mn
6.75
(OH)
3
H
1.20
(VO
4
)
4-2
z
(V
2
O
7
)
z
(
z
= 0.15) experiences ordering into a canted antiferromagnetic state at
T
N
= 42.5 K.
We report on the structural features of Mn
6.75
H
1.20
(VO
4
)
4-2z
(V
2
O
7
)
z
(
z
= 0.15), which clarified the mechanism of negative charge compensation of the framework. The compound undergoes phase transition at
T
N
= 42.5 K into canted AF state.
New nitrosonium manganese(II) nitrate, (NO)Mn
(NO
)
, has been synthesized and structurally characterized. In the temperature range of 45-298 K, the crystal is hexagonal (centrosymmetric sp. gr.
6
/
...). Mn
ions are assembled into tubes along axis
with both NO
filling and coating. The nitrosonium cation is located in the framework cavity and is disordered by a 3-fold axis. At the temperature
= 190 K, a structural phase transition related to the libration of the intertube NO
group and a small variation of Mn polyhedron is observed. Moreover, the anomalies in physical properties of (NO)Mn
(NO
)
allow suggesting that ordering of NO
units occurs at low temperatures. The antiferromagnetic ordering in this compound is preceded by the formation of a short-range correlation regime at about 25 K and takes place in two steps at
= 12.0 K and
= 8.4 K.
New nitrosonium manganese(II) nitrate, (NO)Mn6(NO3)13, has been synthesized and structurally characterized. In the temperature range of 45–298 K, the crystal is hexagonal (centrosymmetric sp. gr. ...P63/m). Mn2+ ions are assembled into tubes along axis c with both NO3 – filling and coating. The nitrosonium cation is located in the framework cavity and is disordered by a 3-fold axis. At the temperature T S1 = 190 K, a structural phase transition related to the libration of the intertube NO3 group and a small variation of Mn polyhedron is observed. Moreover, the anomalies in physical properties of (NO)Mn6(NO3)13 allow suggesting that ordering of NO+ units occurs at low temperatures. The antiferromagnetic ordering in this compound is preceded by the formation of a short-range correlation regime at about 25 K and takes place in two steps at T N1 = 12.0 K and T N2 = 8.4 K.
Anhydrous copper tellurite sulfate, Cu
TeO
(SO
)
, has been synthesized
vapor transport reactions in sealed silica glass ampoules. In measurements of magnetization
, magnetic susceptibility
, ...specific heat
and X-band electron spin resonance, a long-range antiferromagnetic order at
= 13 K and an
-
magnetic phase diagram have been established. One-third of Cu
ions were found to form magnetically silent dimers. A peak in dielectric permittivity
, which accompanies the Néel order, allows considering Cu
TeO
(SO
)
as a magnetoelectric multiferroic material of the second type. Density functional theory calculations provided estimations of leading exchange interaction parameters.
Anhydrous copper tellurite sulfate, Cu3TeO3(SO4)2, has been synthesized via vapor transport reactions in sealed silica glass ampoules. In measurements of magnetization M, magnetic susceptibility χ, ...specific heat Cp and X-band electron spin resonance, a long-range antiferromagnetic order at TN = 13 K and an H–T magnetic phase diagram have been established. One-third of Cu2+ ions were found to form magnetically silent dimers. A peak in dielectric permittivity ϵ, which accompanies the Néel order, allows considering Cu3TeO3(SO4)2 as a magnetoelectric multiferroic material of the second type. Density functional theory calculations provided estimations of leading exchange interaction parameters.
One of the little-studied ways that climate warming or temperature increases in aquaculture could affect aquatic animals is through accelerated aging. This study is dedicated to understanding the ...principles of molecular and cellular aging in the target tissues of juvenile whitefishes (Yenisei hump-snout whitefish and its hybrid) under the influence of acute heat stress (up to 26 °C), and the effects of thermal preconditioning as pre-adaptation. Non-adapted stressed hump-snout whitefish showed a higher induction threshold for functionally active mitochondria in the blood and a decrease in telomerase activity in the liver after heat shock exposure as a long-term compensatory response to prevent telomere shortening. However, we observed heat-induced telomere shortening in non-adapted hybrids, which can be explained by a decrease in mitochondrial membrane stability and a gradual increase in energy demand, leading to a decrease in protective telomerase activity. The pre-adapted groups of hump-snout whitefish and hybrids showed a long-term or delayed response of telomerase activity to heat shock, which served as a therapeutic mechanism against telomere shortening. We concluded that the telomerase and telomere responses to thermal stress demonstrate plasticity of tolerance limits and greater stability in hump-snout whitefish compared with hybrids.
The venom of the black widow spider (BWSV) ( Latrodectus mactans tredecimguttatus ) contains several potent, high molecular mass (>110 kDa) neurotoxins that cause neurotransmitter release in a ...phylum-specific
manner. The molecular mechanism of action of these proteins is poorly understood because their structures are largely unknown,
and they have not been functionally expressed. This study reports on the primary structure of -latroinsectotoxin ( -LIT), a novel insect-specific toxin from BWSV, that contains 1214 amino acids. -LIT comprises four structural domains: a signal peptide followed by an N-terminal domain that exhibits the highest degree
of identity with other latrotoxins, a central region composed of 15 ankyrin-like repeats, and a C-terminal domain. The domain
organization of -LIT is similar to that of other latrotoxins, suggesting that these toxins are a family of related proteins. The predicted
molecular mass and apparent mobility of the protein ( 130 kDa) encoded in the -LIT gene differs from that of native -LIT purified from BWSV ( 110 kDa), suggesting that the toxin is produced by proteolytic processing of a precursor. MALDI-MS of purified native -LIT revealed a molecular ion with m/z + of 110916 ± 100, indicating that the native -LIT is 991 amino acids in length. When the full-length -LIT cDNA was expressed in bacteria the protein product was inactive, but expression of a C-terminally truncated protein containing
991 residues produced a protein that caused massive neurotransmitter release at the locust neuromuscular junction at nanomolar
concentrations. Channels formed in locust muscle membrane and artificial lipid bilayers by the native -LIT have a high Ca permeability, whereas those formed by truncated, recombinant protein do not.
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